The ability of ozone, paraquat, and high levels of oxygen to induce pulmonary fibrosis in rats will be tested. The best agent will be used for a detailed study of the changes in collagen synthesis and/or degradation which take place in fibrotic lungs. Newly synthesized collagen will be analyzed by labelling with radioactive precursor amino acids. Synthesis and degradation of total collagen will be determined by assaying radioactive hydroxyproline. The different types of collagen present will be separated and quantitated, using differential salt precipitation, acrylamide gel electrophoresis, ion-exchange chromatography and cyanogen bromide fragmentation of peptides. It is hoped that this study will provide insight into the role of collagen synthesis and degradation in the etiology of pulmonary fibrosis, which can result from exposure to various toxic agents.